Topics

Topics provide scalable, decoupled, asynchronous messaging between services. When a message is published to a topic, it's immediately pushed to all subscribers, making topics perfect for real-time event processing.

Quick Start

Here's a minimal example to get you started:

import { topic } from '@nitric/sdk'

const userCreatedTopic = topic('user-created').allow('publish')

// Publish a message
await userCreatedTopic.publish({
  email: 'new.user@example.com',
})

// Subscribe to messages
userCreatedTopic.subscribe(async (ctx) => {
  const { email } = ctx.req.json()
  console.log(`New user created: ${email}`)
})

Core Concepts

Topics

A topic is a named resource where events can be published. Topics enable real-time communication between services, with messages being pushed to subscribers as soon as they're published.

Subscriptions

A subscription is a binding between a topic and a service. When a message is published to a topic, all subscribers receive a copy of the message.

Permissions

Topics require explicit permissions for operations:

• publish: Send messages to the topic
• subscribe: Receive messages from the topic

Common Operations

Publishing Messages

const topic = topic('my-topic').allow('publish')

await topic.publish({
  message: 'Hello subscribers!',
})

Subscribing to Messages

const topic = topic('my-topic')

topic.subscribe(async (ctx) => {
  const { message } = ctx.req.json()
  console.log(`Received: ${message}`)
})

Cloud Provider Support

Each cloud provider comes with a set of default services used when deploying resources. You can find the default services for each cloud provider below.